WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
L–2 Copyright © 1998 General Motors Corp.
APPENDIX L — EXTERNALLY-GENERATED ELECTRONIC INTERFERENCE
D. Radio Wiring and Connector Location
(cont’d)
3. Any negative lead from a handset or control unit must return to battery negative.
4. Connect the positive lead from a handset or control unit directly to battery.
5. Fuse handset or control unit positive and negative leads separately from the transceiver
negative and positive leads. Use correctly rated fuses.
E. Power and Ground Wire Routing
Route radio power and ground wires as far away as possible from electronic control modules.
F. Troubleshooting
The following are common causes of EMI/RFI problems:
•
Power leads connected to points other than the battery
•
Improper antenna location
•
Poor shielding or connections to antenna cable
•
Transmitter or transceiver wiring too close to vehicle electronics
1–3. EXTERNALLY-GENERATED SPEED SENSOR SIGNALS
A. Checking for Externally-Generated Speed Sensor Signals
Use the following procedures to determine if speed sensor signals generated by a source external to
the transmission or wiring harness are present:
1. Turn ignition ON.
2. Keep engine OFF.
3. If the ECU is ON (shift selector display remains illuminated), connect the Pro-Link
®
Diagnostic
tool.
NOTE: If false speed signals were present at the previous shutdown, the ECU might still be “on” even though
the ignition is “off.” The Pro-Link
®
is powered by ignition power so the ignition must be “on” to use
the Pro-Link
®
to read the speed signals.
4. Read speed sensor signals.
5. If a speed sensor signal is other than one (1), then there is a short to another circuit that is carrying
an AC signal.
6. Check the resistance of the sensor.
7. Check for shorts to other circuits within the harness or transmission connector.
8. Check to ensure there is no conductive material inside the connector.
9. Check to be sure speed sensor circuit wires are a twisted pair.
10. Check to ensure a properly grounded drain wire.
11. Check for the presence of a strong external AC signal.
12. Repair or replace parts as required.
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